Metal xanthate derivatives



UNITED, STATES PATENT OFFICE,

METAL XANTHATE DERIVATIVES John P. McDcrmott, Roselle, N. J., assignor to Standard Oil Development Company, a corporation of Delaware lilo Drawing. Application September e, 1946, Serial No. 695,281

. 1 This invention relates to a new class of chemical compositions having marked antioxidant properties when incorporated in hydrocarbon products, and it relates more particularly to the use of such compositions in mineral lubricating oils.

In my co-pending application Serial No. 635,112, filed December 14, 1945, and issued as Patent No. 2,436,589 on February 24, 1948, 1 disclosed my discovery that zinc isopropyl xanthate possesses the property of inhibiting the oxida- 11 Claims. (Cl. 260-429) a homogeneous mass, and the product will remain homogeneous on cooling. It is therefore believed that a chemical combination of the two compounds has taken place, and the reaction appears to be one of simple addition, since there 4 is no evidence of the formation of any by-prodtion and consequent development of corrosive properties in mineral lubricating oils to a very remarkable degree, and that the compound also promotes general engine cleanliness when oils containing it are used as crankcase lubricants for internal combustion engines. This agent is free from the corroding tendencies which have been observed when metal derivatives of fatty acids, sulfonic acids, phenols and the like have been used.

One dimculty encountered in the commercial use of zinc isopropyl xanthate as an additive for lubricating oils is the fact that it is diflicult to dissolve much more than about 0.5% by weight of this compound in oil. For many purposes, it would be desirable to employ concentrations greater than 0.5%, and even where this amount or less is required in the oil blend, a compound of increased solubility could be dissolved in an oil in much shorter time and with greater case. It is accordingly an object of the present invention to provide a composition which is a chemical combination of zinc isopropyl xanthate or a similar metal xanthate compound with another compound which markedly increases the solubility in oil and at the same time provides the requisite antioxidant properties. It has been found that zinc isopropyl xanthate and the like may thus be combined with certain metal alkyl and alkaryl thiophosphates and thiophosphites. Such thiophosphate and thiophosphite compounds have already been known as antioxidant and detergent agents for lubricating oils. Such compounds when used alone, however, exhibit a tendency to stain copper and to separate from mineral oil on contact with small quantities of water.

It has been found, in accordance with the present invention, that by heating, a mixture of zinc isopropyl xanthate with a thiophosphate or thiophosphite compound of the type described, e. g., zinc 2-ethy1hexyl thiophosphite at a slightly elevated temperature, of the order of about 110 C., the two compounds will fuse together to form ucts. The reaction may also be brought about by heating the reactants together in an inert organic medium, such as a mineral oil. In preparing compounds or this type it is only necessary to heat the two salts together until a homogeneous solution is obtained, which requires 10 to 15 minutes, and then to filter to remove a slight amount of insoluble material, or to heat the reactants together in the presence of a solvent for the product, such as a mineral lubricating oil, until complete solution has taken place. 1

The adducts" or double salts prepared as described above have been found to be very soluble in mineral oil. In fact, by combining zinc isopropyl xanthate with the thiophosphate or thiophosphite type of salts as described, it has been found that 10% or more of the zinc isopropyl xanthate may be dissolved in the oil. It has also been found that the combination salts exhibit good general antioxidant properties and do not have the copper-staining and water-sensitive characteristics of the metal thiophosphates and thiophosphites. The double salts, in other words, are excellent agents for inhibiting oxidation generally in a wide variety of non-aromatic type hydrocarbon products, as will be disclosed more fully hereinafter.

The metal xanthate compounds which may be employed in accordance with this invention are the metal alkyl xanthates containing metals of groups I and II of the periodic table and have alkyl groups of at least 2 carbon atoms. These alkyl groups may be straight or branched. Such compounds may be prepared by treating an alcohol, e. g., isopropyl alcohol, with potassium or sodium hydroxide and carbon disulflde. 11' a salt of a group 11 metal is desired, the alkali metal xanthate may be reacted with a soluble salt of the metal in question. Examples of such.

metal xanthate compounds are zinc isopropyl xanthate, zinc ethyl xanthate, zinc iso-octyl thioxanthate, potassium butyl xanthate, potassium amyl xanthate, barium cetyl thioxanthate,

and cadmium lauryl xanthate.

The metal thiophosphate and thiophosphite compounds which may be combined with the metal alkyl xanthates in accordance with this through oxygen atoms to phosphorus.

of insoluble material.

. 3 invention are those containing metals of groups I and II and which have formulas in which R represents an alkyl group containing at least 5 carbon atoms or an alkaryl group containing at least 1 alkyl side chain of at least 4 carbon atoms, X represents a, non-metallic element of group VI of the periodic table, M is a metal of group I or group II, and n is a number equal to the valence of the metal. The more preferred compounds are the thiophosphate and thiophosphite compounds containing groups of about 5 to 18 carbon atoms connected Examples of particularly suitable compounds of this type are barium 2-ethylhexyl thiophosphite, barium 2-ethylhexyl thiophosphate, zinc 2-ethylhexyl thiophosphite, and zinc alkyl thiophosphite and thiophosphate in which the alkyl groups are derived from a commercial mixture of and higher alcohols having from 12 to 16 carbon atoms per molecule.

In preparing the combination salts described above it is generally most advantageous to employ from about to about of the xanthate compound in the total salt mixture. The amount oi the final product which is most advantageously employed in lubricating oils and other products will vary according to the purpose in adding the composition and the nature of the basic material;

:but generally when the composition is to be employed as a corrosion 'inhibitor and detergent in crankcase lubricating ofls, the amount is from about 0.02% to about 2%, preferably from 0.1% to 1.0%. For convenient shipping and storage of the additives prior to incorporation in the lubrieating oil base, it is desirable to prepare concentrates containing 25 to 50% of the double salts. When these double salts are prepared by reacting the component salts in an on medium, the reaction product consisting of an oil solution may conveniently be employed as a commercial con- Example 1.Preparation of zinc Z-ethylhexul thiophosphite A mixture of 521 g. of ethyl hexanol and 193 g. oi P431 was heated in a 2-liter 3-necked fiask equipped with a stirrer, reflux condenser, and thermometer for 3 hours at 8090 C., after which the product was filtered to remove a small amount A mixture of 93.6 g. of ZnO in 300 g. of benzol and 150 g. of 99% isopropanol was then added to the filtrate and the composite heated at 50" C. for two hours. The product was then refluxed for 2 hours (78 C.) with stirring, after which it was :filtered, 77.3 g. of residual ZnO being obtained. The solvent was distilled from the product up alkyl to 150 C., after which the residual ZnO was added to the material and the reaction continued at 150 C. for 5 hours. The product was then filtered, and the remaining solvent removed by vacuum distillation. The final product showed the following analysis: 6.94% Zn, 9.56% S. 8.21% P.

Example 2.--Preparati on of barium 2-ethulhexul thiophosphite This preparation was carried out in the same manner as described in Example 1, using 176 g. of BaO. The final product contained 12.79% Ba, 12.23% S, 5.20% P.

Example 3.Preparation of barium 2-ethz lhezyl thiophosphate product contained 15.14% Ba, 7.34% P, and

Example 4.-Preparation of a zinc alkyl' thiophosphate To 214 g. of'a commercial mixture of C12 to C16 alcohols heated to C. in an 800 cc. beaker was added 55.5 g. of P285 in small portions over a period of '1 hour, with stirring. After heating for an additional 2 hours at 95 .C. with nitrogen blowing, the product was filtered to remove a small amount'of insoluble material. The filtrate was then mixed with a slurry of 40.4 g. of ZnO in 150 cc. of benzene, and was gradually heated, with stirring, to 95 C., which temperature was maintained for 4 hours with nitrogen blowing. The product was then filtered and placed on the steam bath with nitrogen blowing overnight. The product contained 5.32% Zn, 10.73% S, 5.45% P.

Example 5.Preparation of a zinc alkyl thz'ophosphite This preparation was carried out in the same manner as described in Example 4, using 69.6 g. of P481. The product contained 3.4% Zn, 7.66% S, and 5.26% P.

Example 6.Preparati0n of zinc tert.-octyl phenyl thiophosphate 413 g. of tert.-octyl phenol (prepared by alkylating phenol with diisobutylene) and 111 g. of P255 were placed in a 3-liter 3-necked flask equipped with a stirrer, reflux condenser and thermometer, and heated at C. for 4 hours. The product was then blown'with nitrogen at 140 C. for 1 hour and then filtered. The filtrate was mixed with 770 g. of a light lubricating oil distillate (SAE 10 grade) and 44 g. of ZnO and then heated for 4 hours at 140-150 C. After blowing with nitrogen for an additional hour at 140 C. the material was filtered. The final oil concentrate comprising 40% of zinc tert.-octyl phenyl thiophosphate in mineral oil, contained 2.03% Zn, 2.35% P and 3.92% S.

Example 7.Preparation of double salts Double salts obtained by reacting zinc isopropyl .xanthate with each of the products prepared in Examples 1 to 6 were prepared by simply heating .parts by weight of the second compound at 100-110 C. with stirring until a homogeneous solution was obtained, which usually required to '15 minutes, and then filtering to remove a slight amount of insoluble material.

In the case of the product obtained in Example 6, the material resulting from the reaction with zinc isopropyl xanthate was an oil' concentrate containing 47% double salt, one fourth of which represented zinc isopropyl xanthate, the net effect being to solubilize the latter salt to the extent of 11.5% .in oil, whereas normally this salt is not soluble to the extent of more than about 0.5% by weight.

Example 8.--Bearing corrosion tests Blends of various individual metal alkyl thiophosphite and thiophosphate compounds prepared as in Examples 1 to 5 and of the double salts prepared by reacting such compounds with zinc isopropyl xanthate, as in Example '1, in a lubricating 011 base were submitted to a corrosion test designed to measure the effectiveness of the products in inhibiting the corrosiveness of a typical mineral lubricating oil toward the surface of copper-lead bearings. The base oil employed was a well refined solvent extracted para-flinic type mineral lubricating oil of SAE viscosity grade, and each blend contained 0.25% by weight of additive. The test was conducted as follows: 500 cc. of the oil was placed in a glass oxidation tube (13 inches long and 2% inches in diameter) fitted at the bottom with a inch air inlet tube perforated to facilitate air distribution. The oxidation tube was then immersed in a heating bath so that the oil temperature was maintained at 325 F. during the test. Two quarter sections of automotive bearings of copper-lead alloy of known weight having a total area of sq. cm. were attached to opposite sides of a stainless steel rod which was then immersed in the test oil and rotated at 600 R. P. 11., thus providing sumcient agitation of the sample during the test. Air was then blown through the oil at the rate of 2 cu. ft. per hour. At the end of each 4-hour period the bearings were removed, washed with naphtha and weighed to determine the amount of loss of corrosion. The bearings were then repolished (to increase the severity of the test), reweighed,

0 carbon lubricating oils but also in conjunction with such detergent type additives as metal sulfonates, metal soaps, metal phenates, metal alcoholates, metal phenol sulfonates, metal alkyl phenol sulfides, metal organo phosphates. thicphosphates, phosphites and thiophosphites, metal salicylates, metal xanthates and thioxanthates, metal thiocarbamates, reaction products of metal phenates or metal phenol sulfides with sulfur, reaction products of metal phenates or metal phenol sulfides with phosphorus sulfides, and the like. Thus, the new additives of this invention may be used in lubricating oils containing such addition agents as nickel oleate, barium octadecylate, calcium phenyl stearate, zinc diisopropyl salicylate, aluminum naphthenate, calcium cetyi phosphate, barium di-tert.-amyl phenol sulfide, calcium petroleum sulfonate, zinc \methyl cyclohexyl thiophosphate, calcium dichlorostearate, etc.

The lubricating oil base stocks used in the compositions of this invention may be straight min- I eral lubricating oils, or distillates derived from and then subjected to the test for additional 4-hour periods in like manner. The results are given in the following table as "corrosion life, which indicates the number of hours required for the bearings to lose 100 mg. in weight, determined by interpolation of the data obtained in the various periods. The unblended base oil showed a corrosion life of 12 hours.

Bearing Corrosion Life, Hrs.

0i] Blend ggzg yi I nc Alone rsopmnyl Xanthate Base 0il+sinc Hthylheryl tbiophosphite. l0 24 Base OiH-barium i-etbylhexyl thiophosphite.. 20 26 Base Oil i-badurn Hthylhexyl thlopbosphate 32 Base Oil-l-sinc slkyl thiopbosphits (product of Exsmnze5).... u-.. i8 26 Base OiH-zinc allryl thiophosphate (product of Example 4) 22 34 Base 0il+zinctsrt.-octyl phenol thiophosphate 29 z;

The products of the present invention may be employed not only as the sole additives in hydroparafiinic, naphthenic, asphaltic or mixed base crudes, or, if desired, various blended oils may be employed as well as residuals, particularly those from which asphaltic constituents have been carefully removed. The oils may be refined by conventional methods using acid, alkali and/or clay or other agents such as aluminum chloride, or they may be extracted oils produced, for example, by solvent extraction with solvents of the type of phenol, sulfur dioxide, furfural, dichloroethyl ether, nitrobenzene, crotonaldehyde, etc. Hydrogenated oils or white oils may be employed as well as synthetic oils prepared, for example, by the polymerization of olefins or by the reaction of oxides of carbon with hydrogen or by the hydrogenation of coal or its products. In certain instances cracking coal tar fractions and coal tar or shale oil distillates may also be used. Also, for special applications, animal, ve etable or fish oils or their hydrogenated or voltolized products may be employed, either alone or in admixture with mineral oils.

For the best results the base stock chosen should normally bethat oil which without the new additives present gives the optimum performance in the service contemplated. ',However, since one advantage of the additives is that their use also makes feasible the employment of less satisfactory mineral oils orother oils, no strict rule can be laid down for the choice of the base stock. Certain essentials must of course be observed. The oil must possess the viscosity and volatility characteristics known vto be required for the service contemplated. The oil must be a satisfactory solvent for the additive, lthough in some cases auxiliary solvent agents may be used. The lubricating oils, however they may have been produced, may vary considerably in viscosity and other properties depending upon the particular use for which they are desired, but they usually range from about 40 to 150 seconds Saybolt viscosity at 210 F. For the lubrication of certain low and medium speed Diesel engines the general practice has often been to use a lubricating oil base stock prepared from naphthenic or aromatic crudes and having a Saybolt viscosity at 210 F. of 45 to seconds and a viscosity index of 0 to 50. However, in certain types of Diesel service, particularly with high speed Diesel engines, and in gasoline engine "service, oils of higher viscosity index are often required, for example "up to 75 or 100. or even may also be used such as dyes, pour depressors,

heat thickened fatty oils, sulfurized fatty oils, organo-metallic compounds, metallic or other soaps, sludge dispersers, antioxidants, thickeners, viscosity index improvers, oiliness agents, defoaming or antifoaming agents, resins, rubber, olefin polymers, voltolized fats, voltolized mineral oils, and/or voltolized waxes and colloidal solids such as graphite or zinc oxide, etc. Solvents and assisting agents, such as esters, ketones, alcohols, aldehydes, halogenated or nitrated compounds, and the'like may also be employed.

Assisting agents which are particularly desirable as plasticizers and defoaming agents are the higher alcohols having eight or more carbon atoms and preferably 12 to carbon atoms. The alcohols may be saturated straight or branched chain aliphatic-alcohols such as octyl alcohol (CaHnOH), lauryl alcohol (CnHaaOH), cetyl alcohol (CmHaaOH), stearyl alcohol, sometimes referred to as octadecyl alcohol (C18H3'IOH), and the like; the corresponding oleflnic alcohols such as' oleyl alcohflircyclic alcohols, such as naphthenic alcohols; and aryl substituted alkyl alcohols, for instance, phenyl octyl alcohol, or octadecyl' benzyl alcohol or mixtures of these various alcohols, which may be pure or substantially pure synthetic alcohols. One may also use mixed naturally occurring alcohols such as those found in wool fat (which is known to contain asubstantial percentage of alcohols having about 16 to 18 carbon atoms) and in sperm oil (which contains a high percentage of cetyl alcohol); and although it is preferable to isolate the alcohols from those materials, for some purposes the wool fat, sperm oil or other natural products rich in alcohols may be used per se. Products prepared synthetically by chemical processes may also be used, such as alcohols prepared by the oxidation of petroleum hydrocarbons, e. g., paramn wax, petrolatum, etc.

The double salts of the present invention are useful as antioxidants in various other hydrocarbon materials, such as extreme pressure lubricants, greases, hydraulic fluids, motor fuels, hydrocarbon polymers, natural and synthetic rubbers, and the like.

The present invention is not to be considered as .limited by any of the examples described herein, which are given by way of illustration only, but is to be limited solely by the terms of the appended claims.

I claim:

1. As a new composition of matter a double salt prepared by fusing together a metal alkyl xanthate, in which the metal is selected from groups I and II of the periodic table and in which the alkyl group contains at least 2 carbon atoms, and a compound selected from the group consisting of metal organo thiophosphites and thiophosphates having the formulas and sents a radical selected from the group consisting of alkyl radicals containing at least 5 carbon atoms and alkaryl radicals containing at least one alkyl side chain of at least-l carbon atoms, X represents a non-metallic element of group VI of the periodic table, M is a metal selected from groups I and II of the periodic table, and n is a number representing the valence of the metal.

2. As a new composition of matter a double salt according to claim 1 in which the metal alkyl xanthate is zinc isopropyl xanthate.

3. As a new composition of matter a double salt prepared by reacting together a metal allwl xanthate in which the metal is a metal of group II of the periodic table and in which thealkyl group contains at least 2'carbon atoms, and a metal alkyl thlophosphate oi the formula in which R is an alkyl group of at least 5 carbon atoms and M is a divalent metal of group II.

4. As a new composition of matter a double salt according to claim 3 in which the metal alkyl xanthate is zinc isopropyl xanthate.

5. As a new composition of matter a double salt prepared by fusing together zinc isopropyl xan-r thate and zinc alkyl thiophosphite, the latter being derived as to its alkyl content from a mixture of C12 to C16 alcohols.

6. As a new composition of matter a double salt prepared by fusing together zinc isopropyl xanthate and zinc alkyl dithiophosphate, the latter being derived as to its alkyl content from a mixture of C1: to Cu alcohols.

7. As a new composition of matter a double salt prepared by fusing together zinc isopropyl xanthate and zinc 2-ethylhexyl thiophosphite.

8. The method of increasing the efiective oil solubility of a metal alkyl xanthate, in which the metal is selected from groups I and II of the periodic table and in which the alkyl group contains at least 2 carbon atoms, which comprises fusing the xanthate salt with a compound selected from the group consisting of metal organo thiophosphites and thiophosphates having the formulas ,5

and

groups I and II of the periodic table, and n is a number equal to the valence of the metal M.

9. The method of increasing the eifective oil solubility of zinc isopropyl xanthate which comprises fusing the same with zinc alkyl dithiophosphate, the latter being derived as to its alkyl content from a mixture of C1: to Cm alcohols.

10. The method according to claim 8 in which respectively, in each of which formulas R repreth wo metal omp nd are h a d her at a temperature of 100 to 110 C. until a homogeneous solution is obtained.

11. The method according to claim 9 in which the two zinc compounds are heated together at a temperature of 100 to 110 C. until a homogene 5 ous solution is obtained.

JOHN P. McDERMO'I'I.

REFERENCES CITED The following references are of record in the file of this patent:

Number 10 UNITED STATES PATENTS Name Date Cadwell Jan. 21, 1923 Sayre Oct. 21, 1924 Cronshaw et a1 Dec. 24, 1929 Mlgrdlchian Apr. 16, 1935 Van Peskl et a1 May '1, 1940 Badertscher et a1. Dec. 24, 1940 Nelson July 25, 1944 Browning July 31. 1945 

1. AS A NEW COMPOSITION OF MATTER A DOUBLE SALT PREPARED BY FUSING TOGETHER A METAL ALKYL XANTHATE, IN WHICH THE METAL IS SELECTED FROM GROUPS I AND II OF THE PERIODIC TABLE AND IN WHICH THE ALKYL GROUP CONTAINS AT LEAST 2 CARBON ATOMS, AND A COMPOUND SELECTED FROM THE GROUP CONSISTING OF METAL ORGANO THIOPHOSPHITES AND THIOPHOSPHATES HAVING THE FORMULAS 